Various systems have been proposed for sensing the fluid pressure in a fluid actuator, such as a double-acting hydraulic cylinder, and communicating such fluid pressure in the form of a control signal to a device for controlling operation of a servo-system of a hydraulic pump, a pressure-compensated flow control valve, and/or the like. In systems wherein a spool-type control valve is employed to effect such fluid signal, the spool must normally move a substantial linear distance which poses packaging as well as leakage problems.
The leakage problem is aggravated in high pressure systems wherein two or more ports are uncovered simultaneously. In addition, such ports generally do not circumvent the valve spool whereby fluid forces are not equally distributed therearound, thus necessitating the use of means to restrain rotation of the spool to effect the desired sensing function. Other systems of this type employed resolver or check valves which tend to complicate the system and also require close calibration.
The present invention is directed to overcoming one or more of the problems as set forth above.